#include "sofa.h"
#include "sofam.h"

int iauGd2gce ( double a, double f, double elong, double phi,
                double height, double xyz[3] )
/*
**  - - - - - - - - - -
**   i a u G d 2 g c e
**  - - - - - - - - - -
**
**  Transform geodetic coordinates to geocentric for a reference
**  ellipsoid of specified form.
**
**  This function is part of the International Astronomical Union's
**  SOFA (Standards of Fundamental Astronomy) software collection.
**
**  Status:  support function.
**
**  Given:
**     a       double     equatorial radius (Notes 1,4)
**     f       double     flattening (Notes 2,4)
**     elong   double     longitude (radians, east +ve)
**     phi     double     latitude (geodetic, radians, Note 4)
**     height  double     height above ellipsoid (geodetic, Notes 3,4)
**
**  Returned:
**     xyz     double[3]  geocentric vector (Note 3)
**
**  Returned (function value):
**             int        status:  0 = OK
**                                -1 = illegal case (Note 4)
**  Notes:
**
**  1) The equatorial radius, a, can be in any units, but meters is
**     the conventional choice.
**
**  2) The flattening, f, is (for the Earth) a value around 0.00335,
**     i.e. around 1/298.
**
**  3) The equatorial radius, a, and the height, height, must be
**     given in the same units, and determine the units of the
**     returned geocentric vector, xyz.
**
**  4) No validation is performed on individual arguments.  The error
**     status -1 protects against (unrealistic) cases that would lead
**     to arithmetic exceptions.  If an error occurs, xyz is unchanged.
**
**  5) The inverse transformation is performed in the function
**     iauGc2gde.
**
**  6) The transformation for a standard ellipsoid (such as WGS84) can
**     more conveniently be performed by calling iauGd2gc,  which uses a
**     numerical code to identify the required a and f values.
**
**  References:
**
**     Green, R.M., Spherical Astronomy, Cambridge University Press,
**     (1985) Section 4.5, p96.
**
**     Explanatory Supplement to the Astronomical Almanac,
**     P. Kenneth Seidelmann (ed), University Science Books (1992),
**     Section 4.22, p202.
**
**  This revision:  2021 May 11
**
**  SOFA release 2021-05-12
**
**  Copyright (C) 2021 IAU SOFA Board.  See notes at end.
*/
{
   double sp, cp, w, d, ac, as, r;


/* Functions of geodetic latitude. */
   sp = sin(phi);
   cp = cos(phi);
   w = 1.0 - f;
   w = w * w;
   d = cp*cp + w*sp*sp;
   if ( d <= 0.0 ) return -1;
   ac = a / sqrt(d);
   as = w * ac;

/* Geocentric vector. */
   r = (ac + height) * cp;
   xyz[0] = r * cos(elong);
   xyz[1] = r * sin(elong);
   xyz[2] = (as + height) * sp;

/* Success. */
   return 0;

/* Finished. */

/*----------------------------------------------------------------------
**
**  Copyright (C) 2021
**  Standards Of Fundamental Astronomy Board
**  of the International Astronomical Union.
**
**  =====================
**  SOFA Software License
**  =====================
**
**  NOTICE TO USER:
**
**  BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND
**  CONDITIONS WHICH APPLY TO ITS USE.
**
**  1. The Software is owned by the IAU SOFA Board ("SOFA").
**
**  2. Permission is granted to anyone to use the SOFA software for any
**     purpose, including commercial applications, free of charge and
**     without payment of royalties, subject to the conditions and
**     restrictions listed below.
**
**  3. You (the user) may copy and distribute SOFA source code to others,
**     and use and adapt its code and algorithms in your own software,
**     on a world-wide, royalty-free basis.  That portion of your
**     distribution that does not consist of intact and unchanged copies
**     of SOFA source code files is a "derived work" that must comply
**     with the following requirements:
**
**     a) Your work shall be marked or carry a statement that it
**        (i) uses routines and computations derived by you from
**        software provided by SOFA under license to you; and
**        (ii) does not itself constitute software provided by and/or
**        endorsed by SOFA.
**
**     b) The source code of your derived work must contain descriptions
**        of how the derived work is based upon, contains and/or differs
**        from the original SOFA software.
**
**     c) The names of all routines in your derived work shall not
**        include the prefix "iau" or "sofa" or trivial modifications
**        thereof such as changes of case.
**
**     d) The origin of the SOFA components of your derived work must
**        not be misrepresented;  you must not claim that you wrote the
**        original software, nor file a patent application for SOFA
**        software or algorithms embedded in the SOFA software.
**
**     e) These requirements must be reproduced intact in any source
**        distribution and shall apply to anyone to whom you have
**        granted a further right to modify the source code of your
**        derived work.
**
**     Note that, as originally distributed, the SOFA software is
**     intended to be a definitive implementation of the IAU standards,
**     and consequently third-party modifications are discouraged.  All
**     variations, no matter how minor, must be explicitly marked as
**     such, as explained above.
**
**  4. You shall not cause the SOFA software to be brought into
**     disrepute, either by misuse, or use for inappropriate tasks, or
**     by inappropriate modification.
**
**  5. The SOFA software is provided "as is" and SOFA makes no warranty
**     as to its use or performance.   SOFA does not and cannot warrant
**     the performance or results which the user may obtain by using the
**     SOFA software.  SOFA makes no warranties, express or implied, as
**     to non-infringement of third party rights, merchantability, or
**     fitness for any particular purpose.  In no event will SOFA be
**     liable to the user for any consequential, incidental, or special
**     damages, including any lost profits or lost savings, even if a
**     SOFA representative has been advised of such damages, or for any
**     claim by any third party.
**
**  6. The provision of any version of the SOFA software under the terms
**     and conditions specified herein does not imply that future
**     versions will also be made available under the same terms and
**     conditions.
*
**  In any published work or commercial product which uses the SOFA
**  software directly, acknowledgement (see www.iausofa.org) is
**  appreciated.
**
**  Correspondence concerning SOFA software should be addressed as
**  follows:
**
**      By email:  sofa@ukho.gov.uk
**      By post:   IAU SOFA Center
**                 HM Nautical Almanac Office
**                 UK Hydrographic Office
**                 Admiralty Way, Taunton
**                 Somerset, TA1 2DN
**                 United Kingdom
**
**--------------------------------------------------------------------*/
}
